The Boeing 777-8X would carry some 350 passengers and could boast the longest range of any commercial aircraft. Reuters reported on Thursday that the aircraft could fly as far as 9,500 nautical miles. A larger version, the 777-9X, would seat about 400 passengers and likely would be the first of the two to enter service, in late 2019.

The 777X is Boeing’s counter to Airbus’ mostly composite A350-1000, which seats 350 passengers in a three-class configuration and 440 in a high-density layout. Airbus plans to deliver the first A350-1000 in 2017, about two years before Boeing would deliver the first 777X.

The larger 777X could “sound the death knell” for Boeing’s quad-engine 747-8. Although the jumbo 747-8 can seat up to 467, its only operator so far, Lufthansa, configures it for no more than 386 passengers.

Boeing widebody jetliners compared

With 787 development nearing an end, Boeing is refreshing the 777, with plans to increase range and efficiency. The planned 777-8X and 777-9X will replace todayís 777-200LR and 777-300ER. The standard 777-200 is likely to be replaced by the 787-10. And the 777-9X could replace the poor-selling 747-8.

* Italicized models are not formally launched development programs, and specifications are speculative.

SOURCES: Boeing, Wikipedia and news reports

Who would buy the 777X?

Dubai-based Emirates, the largest customer of 777s, has expressed interest in buying as many as 100 777Xs. Lufthansa and British Airways also have expressed interest. Longtime loyal Boeing customer Cathay Pacific has ordered A350-1000s but also could be a potential 777X customer.